Which of the Following Statements Is an Example of an Age

Which of the following statements is an example of an age effect?

A) Today's older adults are less likely to seek mental health services because when they were growing up, mental illness was stigmatized.
B) Because exercise has become widely promoted in the media, many older adults are now exercising and thus healthier than was predicted by earlier measures of their physical well-being.
C) Because of the effects of aging on the brain, older adults do less well than younger adults on measures of academic performance.
D) In a longitudinal study, many of the elderly subjects died before the follow-up data was collected.